SR 520 - Floating Bridge and Landings Project - Complete August 2017

OverviewThe SR 520 Floating Bridge and Landings project replaced the original, 53-year-old SR 520 floating bridge as the “world’s longest floating bridge.” The new span across Lake Washington opened to traffic in April 2016.

Below is information about the new SR 520 floating bridge’s benefits. To learn about how the bridge was constructed, check out our SR 520 floating bridge booklet (pdf 6.84 mb).

Summer 2017 – All final, remaining work on the new floating bridge project complete.

Improves Safety
After over a half century of use, the old SR 520 floating bridge was showing its age. The bridge's pontoons were vulnerable to windstorms and its hollow support columns were vulnerable to earthquakes.

The new floating bridge is designed to withstand a 100-year windstorm, and the bridge’s fixed supports on either end have been designed to modern earthquake standards.

Relieves Congestion
The old bridge had only two lanes in each direction, no shoulders and no HOV lanes. The new bridge features two general-purpose lanes and one transit/HOV lane in each direction, and wider, safer shoulders that allow vehicles to pull over in the case of a breakdown.|

Adding transit/HOV lanes, shoulders and a bicycle/pedestrian path provides greater reliability and more options to accommodate growth in the region. The new bridge also has the ability to accommodate light rail if the region chooses to fund it in the future.

Protects Environment
The new floating bridge is designed to capture and filter roadway runoff, which previously drained undiluted off the old floating bridge and into Lake Washington.

The SR 520 Program has also participated in numerous mitigation projects to protect the natural environment of the greater Lake Washington watershed. Learn more about these projects and other environmental benefits on our SR 520 – Environmental Stewardship page.

Partnerships & Cooperation
WSDOT and its contractors worked closely with local, state and federal officials, Native American tribes, regulatory agencies, environmental groups, community organizations, transit agencies and many others during the planning, design and construction of the new SR 520 floating bridge.

Funding

The project was funded by a variety of state and federal sources, including SR 520 tolling that began in December 2011. The final cost of the Floating Bridge and Landings Project, including preliminary engineering and right of way, was approximately $848 million.